Weymouth Mayor Robert Hedlund on Sunday said he was “well aware” of the Facebook post after he and Fire Chief Keith Stark received emails from several upset residents.

“I’m aware of it, and both the fire chief and town counsel are aware of it,” Hedlund said. “There will be more formal discussions about it, and (the chief) plans to initiate an investigation.”

Hedlund declined to identify the firefighter because the authenticity of the post had not been verified Sunday.

The firefighter appeared to have deleted his Facebook account by Sunday afternoon. The post, which several people reportedly captured before it got deleted, criticized use of the life-saving drug Narcan and suggested letting addicts who overdose die. “These losers are out of the hospital and using again in hours, you use you should loose (sic),” the post read.

Even if the post was made from a personal account, Hedlund said it raises concern.

“I’m liberal with my speech on Facebook and speak my mind, and exercise my First Amendment right, but there are certain boundaries and responsibilities that come with the job,” Hedlund said.

Stark could not be reached for an interview Sunday but acknowledged the situation in an email statement.

“The comments posted do not reflect the philosophy or values we hold as a fire department or town,” Stark said. “The incident remains under investigation.”

On-duty firefighters at each of Weymouth’s three fire stations declined to comment Sunday night.

There were 185 confirmed and suspected opioid overdoses resulting in 24 deaths in Weymouth in 2015.

Last month, Weymouth was among 16 Massachusetts communities selected to receive an $85,000 federal grant to implement programs aimed at reducing prescription drug use by young people.

By Sunday night, the post went viral on Twitter and Facebook, generating a deluge of comments from across the country. The Weymouth Firefighters Facebook page was flooded with outcry and outrage from people in California, Delaware and New Jersey, among other locations. People called the post a “disgrace,” “insensitive” and “appalling.”

Melissa Hurley, director of media relations for the Professional Firefighters of Massachusetts, released an initial statement Sunday afternoon on behalf of James Young, union president of the Weymouth Firefighters Local 1616.

The statement expressed disapproval of the post and reassured that the safety of all Weymouth residents is a priority. Later, Hurley said to disregard those initial comments, saying Local 1616 would release a statement directly.

Local 1616 did not release a statement by Sunday evening, and Young could not be reached for comment.